This invention belongs to the field of agricultural chemistry, and provides new herbicides. The growth of weeds, which are plants growing where they are not wanted, has inevitable deleterious effects on crops which are infested with the weeds. Weeds growing in cropland, as well as in fallow land, consume soil nutrient and water, and compete with crop plants for sunlight. Thus, weed plants constitute a drain on the soil and cause measurable losses in yields.
The compounds of this invention are new to organic chemistry. Earlier workers have found herbicides among the pyridazinones, for example, U.S. Pat. No. 3,644,355. Pyrimidine herbicides have also been disclosed, such as the 3-phenyl-4-pyrimidinones of U.S. Pat. No. 3,823,135. The chemical literature shows some diphenyl-5-pyrazolinones, such as the 3-methyl- 1,4-diphenyl compound of Beckh, Ber. 31, 3164 (1898) and the 2-methyl-1,3-diphenyl compound of Knorr et al., Ber. 20, 2549 (1887). Antipyrine, a pharmaceutical pyrazolinone, is 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one. Merck Index, 93 (8th Ed. 1968). DeSarlo et al. taught 2-methyl-4-phenyl-3-isoxazolin-5-ones in Tetrahedron 22, 2989-94 (1966).